1. Field of the Invention
This invention relates to imprinting devices and in particular to bidirectional imprinters suitable for imprinting different fields of data depending upon the direction in which the imprinter is operated.
2. Discussion of the Prior Art
Various bidirectional imprinters are known and have been disclosed in U.S. Pat. Nos. 3,272,120, 3,340,800, 3,577,917, 3,750,569, 3,763,777, 3,810,424 and 3,862,598. In a bidirectional imprinter there is usually critical data which is imprinted onto a document such as an invoice from a portable printing plate such as a credit card. There is also non-critical data imprinted on the invoice from a fixed printing plate such as a dealer's plate. It is important that the critical data be very leglible since it is usually intended for reading by an automatic character recognition device or the like. Since these devices are capable of erroneous character recognition if the data is not imprinted exactly correct, it is desirable to employ a bidirectional imprinter where the critical data is imprinted when the imprinting roller carriage passes over the print bed in a first direction and the non-critical data is imprinted during a pass in the opposite direction. Thus, there is no adverse effect on the quality of the imprinted critical data due to imprinting non-critical data at the same time. The prior art bidirectional imprinters as exemplified by the above patents, have implemented the bidirectional imprinting function with various mechanical arrangements which have not only been complicated but expensive and difficult to maintain.
In U.S. Pat. No. 3,838,641 (which is hereby incorporated herein by reference) there is disclosed an imprinter wherein imprinting pressure is effected by mounting the ends of the print roller shafts into grooves angled with respect to the print bed whereby relative movement of the print roller carriage and the print bed in the imprinting direction forces the shafts to the bottom of the slots whereby imprinting can be effected. The imprinter is not bidirectional.